This invention relates to an oil separator with a casing in which a rotor is rotatably arranged, said rotor having a flow chamber through which oil-laden air can flow and said flow chamber containing a porous material.
In particular, this invention relates to an oil separator for use in an aero gas turbine.
In the prior art, the air flowing through aero gas turbines is passed through an oil separator in order to separate minute oil droplets carried in the air.
Various designs of such oil separators are known in the prior art. For example, these can be provided as stationary elements in vent covers in order to separate the oil particles from the air flow in which they are carried.
In the field of aero gas turbines, separators of the rotor type, as specified above, are known. Here, the porous material contained in the flow chamber or in the blades of the rotor is provided in the form of a metallic spongiose element. This material is commercially available under the brand name RETIMET®, for example. Such metal sponges are made by the application of a vapour coat or the deposition of metallic materials, such as nickel or chrome-nickel alloys, on plastic bases. The spongiose plastic bases are subsequently removed, which results in a porous latticework element. This element is machineable mechanically, can be formed into a great variety of shapes and features good mechanical strength properties.
In the case of centrifugal oil separators of the type according to this invention, the oil-laden air passes the rotating flow chamber, in which the oil-laden air is subjected to centrifugal or centripetal forces. Due to their difference in mass, the air particles and the fine oil particles are subject to different forces. The oil particles are moved radially outward by centrifugal action and unite with other oil particles, finally forming minute droplets which can be discharged from the rotor.
In the case of aero gas turbines, the passing air will be laden with oil, particularly in the bearing areas where the suction force of the airflow removes bearing oil. Separation of oil from the air is not only desirable for environmental reasons but also for re-feeding the separated oil into the lube-oil circulation system.
A disadvantage of the known types of oil separators lies in their inability to remove the finest oil particles from the air. Accordingly, the discharging air is still laden with oil mist or oil fog, which is visible to passengers or airport personnel as oil fog exiting from the engine and which may lead to irritations.